Yes some interesting flys apparently but told we can't divulge any details about it on a public forum - I guess until the work is published in the scientific literature.
My own 'survey' revealed swarms of Daphnia (prob Daphnia magna) last year in the first flash when I was taking salinity samples. These are relatively large 'Water Fleas' (crustaceans) and I'm gessing would be a good meal for an Avocet. The concentration of them last summer was impressive - about 10 individuals per 50ml (200 per litre) would be my estimate. I posted a photo of them on this forum at the time.
Thanks Dave.
For me I'm afraid flies are only interesting if they bring interesting birds.:-O
I think Daphnia is probably a good call for the Avocet menu (I didn't know they were tolerant to brackish waters so hadn't thought). Easy enough to monitor and, being "well-known" it's probably possible to encourage if necessary too so that's comforting.
Paul